Why Can Twins Share A Zodiac Sign — But Act Totally Different?

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Mary-Kate's the sporty one. Ashley's the girly one. Brie is an earth child while Nikki's all glam. No matter how much they look alike, twins can behave like polar opposites — which can be a bit of a conundrum if you're new to astrology. After all, when we first learn about the signs of the Zodiac, we're taught that they each have a specific set of likes, dislikes, and personality traits that define them. How, then, can two people with not just the same sign but the same birthday (in most twins' cases) act so differently?
As is usually the case in astrology, it all comes down to the siblings' birth charts, which show the sun, moon, and planets' positions in the sky at the moment of birth. If you've ever looked up your own birth chart or had it read by an astrologer, you already know that you must provide your birth date, time, and place in order to have it drawn up. Although your birth date and place alone can reveal plenty about your astrological identity, you absolutely need to know your birth time (to the minute) to know your rising sign, or the sign that was aligned with the eastern horizon when you were born.
Also known as your ascendant sign, your rising sign is foundational to your personality. It determines the type of first impression you normally make and others' perception of you — and it just might be the key factor in "polar opposite" twin duos.
"A couple of minutes changes the ascendant degree," astrologer Amy Tripp says. In other words, you need to know your exact birth time because the sign that's coming up on the horizon changes very frequently — roughly every two hours. So, depending how close the current rising sign is to switching, it's possible for twins to be born only a few minutes apart and end up with different rising signs. And, even though that's one difference in two otherwise identical charts, this would be enough to make them seem very different in person.
For example, if one twin was born in the final moments that Leo is on the horizon and the second was born late enough for their rising sign to be Virgo, you can bet they'd give radically different first impressions. Where the former likely projects a big personality and draws others to them the moment they enter a room, the latter probably seems a little more selfless, withdrawn, and even anxious.
But, even if a pair of twins share their rising sign, there's no astrological reason for their personalities to be carbon copies. You probably don't behave just like someone who happens to share your sign, and the same goes for siblings that share planetary placements. Come to think of it, maybe that "set" of personality traits we mentioned earlier is less of a checklist and more of a spectrum: No two Scorpios, for example, exhibit the same exact traits in the same exact way. So, even with all the same signs between them, there's a pretty big chance that two twins will express them differently. If you need more proof, just watch a few episodes of So Little Time.